In recent years, a buckling restrained brace has been adopted as an axial member used as a brace, for example, of a building or a bridge structure. In the buckling restrained brace, a core material receiving an axial force is restrained from an outer peripheral side by a steel tube and concrete or mortar. Therefore, the buckling restrained brace is prevented from out-of-plane deformation or buckling and deforms plastically, thereby enhancing aseismic and vibration control performances of the building or the bridge structure.
An example of a buckling restrained brace is disclosed in Patent Literature 1, where buckling strength of a core material is improved by a first reinforcing member and a second reinforcing member.